Radiative anti-parity-time plasmonics

Abstract

Space and guided electromagnetic waves, as widely known, are two crucial cornerstones in extensive wireless and integrated applications respectively. To harness the two cornerstones, radiative and integrated devices are usually developed in parallel based on the same physical principles. An emerging mechanism, i.e., anti-parity-time (APT) symmetry originated from non-Hermitian quantum mechanics, has led to fruitful phenomena in harnessing guided waves. However, it is still absent in harnessing space waves. Here, we propose a radiative plasmonic APT design to harness space waves, and experimentally demonstrate it with subwavelength designer-plasmonic structures. We observe two exotic phenomena unrealized previously. Rotating polarizations of incident space waves, we realize polarization-controlled APT phase transition. Tuning incidence angles, we observe multi-stage APT phase transition in higher-order APT systems, constructed by using the scalability of leaky-wave couplings. Our scheme shows promise in demonstrating novel APT physics, and constructing APT-symmetry-empowered radiative devices.

Recent advances of transition radiation: Fundamentals and applications

“…Particularly, the influence of optical gain and the slab thickness on the directionality of transition radiation remains elusive, while a larger optical gain is generally thought to have a larger enhancement of the intensity of transition radiation. More rich physics of free-electron radiation could be expected in systems simultaneously with optical gain and optical loss, such as those with parity-time symmetry [183][184][185][186][187]. However, the influence of the interplay between optical gain and optical loss on the transition radiation has never been explored before.…”

Dynamic Optical Encryption Fueled via Tunable Mechanical Composite Micrograting Systems

“…Optical encryption provides a promising route for information security owing to the unique advantages of satisfactory flexibility introduced by multiple regulable physical characteristics of light. [6] Micro/nanostructured functional surfaces, such as photonic crystals, [7][8][9][10][11] surface plasmon, [12] metasurfaces, [13,14] have powerful light manipulation ability by altering the amplitude, [15,16] phase, [17][18][19][20] polarization, [21] and hybrid parameters [22][23][24] of light, which are well-suited for the field of optical encryption. Owing to the advantages of compact size, low power consumption, and inherent difficulty in replication, micro/nanostructured functional surface-based optical devices are highly desirable for a variety of uses, such as metalens, [25,26] anticounterfeit tags, [27] visible camouflage.…”

Harnessing Anti‐Parity‐Time Phase Transition in Coupled Topological Photonic Valley Waveguides

“…[ 5–7 ] More specifically, the most striking property of a topological system is its robust edge/interface states that are resilient to structural imperfections, [ 8–11 ] enabling applications in robust optoelectronic devices, [ 5 ] while a system respects PT symmetry, exhibiting non‐Hermitian phase transitions, [ 6,7 ] provides fascinating approaches for manipulating light strengths or spectral line shapes. [ 6,7 ] The recently emerging anti‐parity‐time (APT) symmetry has also attracted much attention, [ 12–32 ] and resulted in interesting applications, e.g., mode switching, [ 18,32 ] optical routers, [ 24 ] and ultrasensitive sensing. [ 20,26,28 ]…”

“…We theoretically reveal and experimentally demonstrate that the coupling between two TVWs renders an APT phase transition in the spectral domain, unlike conventional APT approaches that exploit dissipative/nonlinear processes. [ 12–32 ] In coupled topological valley waveguides (CTVWs), one waveguiding direction (− z channel) works for the evolution of the topological modes, and the opposite direction (+ z channel), which is not utilized in conventional waveguide arrays, is used as an effective dissipation channel (as illustrated in Figure 1c). The valley topology protects the light propagations in both APT phases with near‐vanished intervalley scattering from the joints between the CTVW and uncoupled TVWs.…”